The world is at risk of losing hard-won gains in fighting Covid-19 as the highly transmissible Delta variant spreads, but WHO-approved vaccines remain effective, the World Health Organization (WHO) said on Friday.

The US Centers for Disease Control and Prevention (CDC) has described the Delta variant of the coronavirus as being as transmissible as chickenpox and cautioned it could cause severe disease, the Washington Post said, citing an internal CDC document.

Covid-19 infections have increased by 80 percent over...